The phytopathogenic fungus Ashbya gossypii is a filamentously growing ascomycete that was first isolated as a plant pathogen in tropical and sub-tropical regions. It infects the seed capsule of cotton plants (Ashby S. F. and Nowell W. (1926) Ann. Botany 40: 69-84) and has also been isolated from tomatoes and citrus fruits (Phaff H. J. and Starmer W. T. (1987) In "The Yeasts", Vol. I Rose A. H., Harrison, J. S. (eds), Academic Press, London, 123 ff; Dammer K. H. and Ravelo H. G. (1990). Arch. Phytopathol. Pflanzenschutz, Berlin 26: 71-78 Dammer and Ravelo, 1990). The infection of the seed capsule is caused by transmission of A. gossypii mycelium pieces or spores by stinging-sucking insects and causes a disease called stigmatomycosis.
Studies characterising the karyotype of A. gossypii have been performed (Wright, 1990; Wendland, 1993; Gaudenz, 1994, "The small genome of the filamentous fungus Ashbya gossypii: Assessment of the karyotype", Diploma Thesis, Department of Applied Microbiology, Biocenter, University Basel). It has been found using yeast chromosomes of precisely known length as size markers that the genome of A. gossypii has a total nuclear genome size of 8.85 Mb. Presently, A. gossypii represents the most compact eukaryotic genome, compared to genome sizes of 12.5 Mb for Saccharomyces cerevisiae (Chu et al. (1986) Science, 234:1582-1585), 31.0 Mb for Aspergillus nidulans (Brody and Carbon (1989) Proc Natl Acad Sci USA. 86:6260-6263), and 47.0 Mb for Neurospora crassa (Orbach et al.(1988) Mol Cell Biology, 8:1469-1473).
A. gossypii is systematically grouped to the endomycetales belonging to the family of spermophthoraceae. This classification is based on the observation that the spores that develop in hyphal compartments called sporangia look like ascospores, which are defined as end products of meiosis.
Since A. gossypii is a filamentous ascomycete, and is capable of growing only by filamentous (hyphal) growth, fungal targets found in this model organism are predictive of targets which will be found in other pathogens, the vast majority of which grow in a filamentous fashion.